The present invention relates to semiconductor structures, and particularly to a metal-oxide-semiconductor field effect transistor (MOSFET) having at least one self-aligned diffusion contact and methods of manufacturing the same.
As semiconductor devices shrink in each generation of semiconductor technology, formation of contact structures to source and drain regions of a field effect transistor become challenging because such contact structures not only need to provide reliable electrical contact to the source and drain regions, but also need to avoid electrically shorting to other components such as the gate electrode of the field effect transistor. Since the etch chemistry employed for the anisotropic etch process remains the same while the lateral dimension of the dielectric gate spacer shrinks with the scaling of semiconductor devices, the likelihood of excessive removal of the dielectric gate spacer within the normal range of process variations during the anisotropic etch increases as the dielectric gate spacer becomes thinner in each technology generation. Excessive removal of the dielectric gate spacer increases the probability of an electrical short between a contact to the source region or the drain region of a field effect transistor and the gate electrode of the field effect transistor. Thus, the possibility of excessively thinning the dielectric gate spacer during the anisotropic etch for forming contact vias is a significant concern for product yield and reliability purposes.